chore: nightly sync main into dev (02_07_2026)

[svcnvidia-nemo-ci]

Summary

Nightly sync of main into dev for 02_07_2026.

• 73 commits from main merged into dev.
• Python lines: +10208 / -1247 across 92 files (excludes golden-value JSON, uv.lock, etc.).
• 61 files had merge conflicts, resolved surgically (see below).

Merge strategy

Started from origin/dev and ran git merge origin/main --no-edit, then resolved
each conflict preserving recent dev-only additions while incorporating main's
incoming changes. The dev-feature-preservation pre-push guard passes (no dev-only
code silently dropped).

Per the nightly-sync policy, the sync is dev-preferring for shared code that both
branches evolved: where main refactored/reorganized code dev also touched, dev's
version is kept to protect in-flight dev work; main's genuinely-new files, symbols and
features are brought in. This keeps the dev-feature-preservation guard green.

Files taken from main (override list)

These files reference dev-only args/APIs that were reconciled by taking main's version:

• megatron/training/training.py — took main's version; renamed
  args.hybrid_context_parallel → args.dynamic_context_parallel to match the merged
  args namespace (dev's arg name; hybrid_context_parallel is a deprecated config alias).
• megatron/training/initialize.py — main's version; already uses
  dynamic_context_parallel / min_dynamic_context_parallel_size, consistent with the
  merged parallel_state.initialize_model_parallel signature.

Dependency triple + CODEOWNERS

Kept dev's pyproject.toml, uv.lock, docker/Dockerfile.ci.dev, and .github/CODEOWNERS
verbatim (verified byte-identical to origin/dev). Git-source reconciliation: main adds a
mamba-ssm git source and bumps flash_mla/transformer-engine/emerging_optimizers;
dev pins mamba-ssm~=2.2 from PyPI and is ahead on emerging_optimizers (v0.3.0). No
merged main code was found to require a symbol only present at main's git revisions, so
dev's triple is kept unchanged.

API-mismatch fixes

• megatron/training/checkpointing.py (kept dev's) — added dp_group, expt_dp_group,
  and rng_state_key_prefix compatibility parameters to save_checkpoint / load_checkpoint
  so main's training.py process-group-threaded call sites work against dev's checkpoint path.
• .github/copy-pr-bot.yaml — merged the trustees list as a union (kept dev-only
  wplf plus main's newly-added trustees).
• Restored dev's test_fused_mla_training_hooks_use_fused_down_projection unit test
  (verified it passes against the merged FusedMLASelfAttention.backward_dw →
  _backward_output_proj → linear_proj.backward_dw call chain).

Files deleted in dev and intentionally NOT restored

Verified each was deleted intentionally on dev (or removed by main) and nothing in the
merged tree imports them:

• .github/workflows/multi-approval-bot.yml — dev removed the multi-approval action (ci: Remove multi-approval action from dev branch #3576).
• tests/test_utils/recipes/h100/bert.yaml, t5.yaml — dev refactored functional tests.
• tests/unit_tests/inference/engines/test_cg_admission_gating.py — dev deleted it;
  the merged engine does not expose the _cg_admission_gating_active / _cg_admission_check
  methods the test requires.

Remerge diff

git show --remerge-diff HEAD on the merge commit is large; a summary of the conflict
resolutions is captured above. The full conflict set spanned 61 files across training,
core transformer, MoE, DSA/experimental attention, RL, FSDP, inference, and their tests.

[svcnvidia-nemo-ci]

/ok to test cd117b3

[svcnvidia-nemo-ci]

/ok to test d086376

[svcnvidia-nemo-ci]

/ok to test 5871bc8

[svcnvidia-nemo-ci]

/ok to test e2dce1e